Many beneficial devices or structures in myriad applications rely on batteries as a power source. A typical liquid-cell battery, such as battery 101 in FIG. 1, is characterized by an electrolyte liquid 102 which provides a mechanism for an electrical charge to flow in direction 103 between a positive electrode 104 and a negative electrode 105. When such a battery 101 is inserted into an electrical circuit 106 with illustrative load 108, it completes a loop which allows electrons to flow in direction 107 around the circuit 106. The positive electrode 104 thus receives electrons from the external circuit 106. These electrons then react with the materials of the positive electrode 104 in reduction reactions that generate the flow of a charge to the negative electrode 105 via ions in the electrolyte liquid 102. At the negative electrode 105, oxidation reactions between the materials of the negative electrode 104 and the charge flowing through the electrolyte fluid 102 result in surplus electrons that are released to the external circuit 106.
As the above process continues, the active materials of the positive and negative electrodes 104 and 105, respectively, eventually become depleted and the reactions slow down until the battery is no longer capable of supplying electrons. At this point the battery is discharged. It is well known that, even when a liquid-cell battery is not inserted into an electrical circuit, there is often a low level reaction with the electrodes 104 and 105 that can eventually deplete the material of the electrodes. Thus, a battery can become depleted over a period of time even when it is not in active use in an electrical circuit. This period of time will vary depending on the electrolyte fluid used and the materials of the electrodes.
More recently, batteries having at least one nanostructured surface have been proposed wherein nanostructures are used to separate the electrolyte from the electrode until such a time that the battery is to be used. This is typically referred to as a reserve battery (as opposed to a primary battery that is manufactured with the electrolyte in contact with the electrodes of the battery). An example of the use of electrowetting principles applied to reserve batteries is described in copending U.S. patent application Ser. No. 10/716,084 filed Nov. 18, 2003 and entitled “Electrowetting Battery Having Nanostructured Surface,” which is hereby incorporated by reference herein in its entirety. As disclosed in the '084 application, when it is desired that the battery generate a current, the electrolyte is caused to penetrate the nanostructured surface and to come into contact with the electrode of the battery, thus resulting in the above-discussed flow of electrons around a circuit. Such a penetration of nanostructures is achieved, for example, by applying a voltage to the nanostructures such that the contact angle of the electrolyte relative to the nanostructured surface is decreased. When the contact angle is decreased, the electrolyte penetrates the nanostructures and is brought into contact with the electrode.